Cryogen pump

ABSTRACT

A cryogen pump, including: a pump section that includes: a bellow with an inlet opening at a first end and an exit opening, the inlet opening in direct fluid communication with a volume of a cryogen, the exit opening at least in fluid communication with a second end of the bellow opposing the first end, a pair of plugs configured to sealingly close the opposing ends of the bellow, the pair of plugs cooperating so that when one plug sealingly closes one of the ends, the other end of the bellow is open; and a drive section configured to drive the pump section in a reciprocating manner so as to move the plugs.

BACKGROUND

1. Field of the Invention

Embodiments of the present invention relate generally to cryogenic pumpsand, more particularly, to submerged or insulated cryogenic pumps.

2. Description of Related Art

Handling cryogen fluid at, or slightly below its boiling temperature,which is well below room temperature, can be cumbersome due to thecreation of two-phase Condition with any heat absorbed from theenvironment. Liquid nitrogen, as a cryogen, has additional handlingdifficulties associated with the Leidenfrost effect and the 700 foldvolume expansion from liquid to gas.

As is conventionally known, liquid nitrogen has characteristics thatmake it difficult to fill a volume. This difficulty is due to theLindenfrost effect, by which a cushion of vapor results whenever theliquid comes into contact with a surface with a temperature higher thanthe boiling temperature.

The change of pressure may be another source of difficulties related tothe physical state of the fluid. First, it makes it difficult to pressthe fluid since gaseous phase is compressible. Second, other effect isbehavior of liquid nitrogen under vacuum condition. It is very difficultto suck liquid nitrogen. Under vacuum conditions, the boilingtemperature decreases, which make the surface temperature higher thanthe boiling temperature and the above-mentioned effect, come again intoplay.

One approach to compensate for these issues is the strategic selectionof components for fluid cryogenic system.

Applying bellows for several fluid systems components is known.

For example, bellow valves are disclosed in U.S. Patent Publication No.2011/0067879 A1 and U.S. Pat. No. 4,838,462. Dispensing fluid from abottle or container is disclosed in International Patent PublicationNos. WO 94/07113, and WO 97/15223.

The application of a bellow for pumping liquid is disclosed in, forexample, the following U.S. Pat. Nos. 3,598,505; 4,310,104; 4,817,688;4,902,206; 5,165,866; 5,308,230; and 5,655,893. The application of abellow for pumping liquid is also disclosed in, for example, thefollowing U.S. Patent Publications: US2004/0265149 A1; US 2005/0031475A1; 2006/0165541 A1; and 2011/0318207 A1, as well as InternationalPatent Publication WO 01/91911 A1.

Further, submerged pumps are disclosed in, for example, U.S. Pat. Nos.4,472,946, and 4,860,545. A bellow submerged pump is disclosed in, forexample, U.S. Pat. No. 7,192,426 B2.

A vacuum bellows is disclosed in U.S. Patent Application No. 6,268,995B1.

In these examples of related art, the main emphasis was on themechanisms for pumping force and efficiency of the motion. However theapplication of simple check valves for controlling the inlet and outletfluid is common.

The foregoing is intended to be illustrative discussion rather anexhaustive one.

BRIEF SUMMARY

Embodiments of the present invention provide an approach by which theinlet valve and suction condition are eliminated. Filling of a cylinderor a bellow with the pumped cryogenic liquid such as liquid nitrogen isdone by creating conditions of communicating vessels, i.e. bygravitational force, without suction, or the need to lower pressure inthe cylinder or the bellow, bellow the atmospheric pressure, or thepressure of the filling tank. Additionally, embodiments of the presentinvention reduce or eliminate the effect of the ambient temperature byvacuum insulating the cylinder or the bellow, thus eliminating the needto submerge the pumping unit into the cryogenic liquid.

An aspect of the present invention provides a cryogen pump having: apump section that includes: a bellow with an inlet opening at a firstend and an exit opening, the inlet opening in direct fluid communicationwith a volume of a cryogen, the exit opening at least in fluidcommunication with a second end of the bellow opposing the first end, apair of plugs configured to sealingly close the opposing ends of thebellow, the pair of plugs cooperating so that when one plug sealinglycloses one of the ends, the other end of the bellow is open; and a drivesection configured to drive the pump section in a reciprocating mannerso as to move the plugs.

Another aspect of the present invention provides a cryogen pump having:a pump section that includes a cylinder having an inlet opening incommunication with a cryogen and an exit valve, a piston configured totravel reciprocally in the cylinder along a travel axis therein betweena load condition in which the piston is at a position of minimumdisplacement and the cryogen flows into the cylinder via the inletopening and a compressing condition in which the piston is at a positionof maximum displacement, cryogen does not flow into the cylinder, andcryogen in the cylinder is compressed and pressed out of the exit valve;and a drive section configured to drive the pump section in areciprocating manner so as to move the piston.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is neither intended to identify key featuresor essential features of the claimed subject matter, nor should it beused to limit the scope of the claimed subject matter. Furthermore, theclaimed subject matter is not limited to implementations that solve anydisadvantage noted in any part of this application.

The aforementioned and/or other features, aspects, details, utilities,and advantages of the present invention are: set forth in the detaileddescription which follows and/or illustrated in the accompanyingdrawings; possibly inferable from the detailed description and/orillustrated in the accompanying drawings; and/or learnable by practiceof the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more readily understood from the detaileddescription of embodiments thereof made in conjunction with theaccompanying drawings of which:

FIG. 1. is a schematic cross-sectional view of a pumping unit consistentwith an exemplary embodiment of the present invention;

FIG. 2. is a schematic cross-sectional view of a pumping unit consistentwith another exemplary embodiment of the present invention;

FIG. 3. is a schematic cross-sectional view of a pumping unit consistentwith another embodiment of the present invention;

FIG. 4A is a schematic cross-sectional view of a pumping unit consistentwith an embodiment of the present invention; and

FIG. 4B is detailed schematic cross-section view of the piston seen inFIG. 4A;

FIG. 5A is a schematic cross-sectional view of a pumping unit consistentwith another embodiment of the present invention; and

FIG. 5B is detailed schematic cross-section view of the piston seen inFIG. 5A;

FIG. 6A is a schematic illustration of a piston optionally usable in anyof the pumping units of FIGS. 4A and 5A; and

FIG. 6B is detailed schematic cross-section view of the piston seen inFIG. 6A;

FIG. 7 is a schematic cross-sectional view of an alternative drivingsection that is optionally usable in any of the pumping units of FIGS.1-3, 4A and 5A; and

FIG. 8 is a schematic cross-sectional view of yet another alternativedrive section that is optionally usable in any of the pumping units ofFIGS. 1-3, 4A and 5A.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The embodiments are described below to explain the presentinvention by referring to the figures.

The drawings are generally not to scale. For drawing clarity,non-essential elements may have been omitted from some of the drawings.

Although the following text sets forth a detailed description of atleast one embodiment or implementation, it is to be understood that thelegal scope of protection of this application is defined by the words ofthe claims set forth at the end of this disclosure. The detaileddescription is to be construed as exemplary only and does not describeevery possible embodiment since describing every possible embodimentwould be impractical, if not impossible. Numerous alternativeembodiments and/or implementations are both contemplated and possible,using either current technology or technology developed after the filingdate of this patent, which would still fall within the scope of theclaims.

It is to be understood that, unless a term is expressly defined in thisapplication using the sentence “As used herein, the term ‘ ’ is herebydefined to mean . . . ” or a similar sentence, there is no intent tolimit the meaning of that term, either expressly or by implication,beyond its plain or ordinary meaning, and such term should not beinterpreted to be limited in scope based on any statement made in anysection of this patent (other than the language of the claims). To theextent that any term recited in the claims at the end of this patent isreferred to in this patent in a manner consistent with a single meaning,that is done for sake of clarity only so as to not confuse the reader,and it is not intended that such claim term be limited, by implicationor otherwise, to that single meaning. Finally, unless a claim element isdefined by reciting the word “means” and a function without the recitalof any structure, it is not intended that the scope of any claim elementbe interpreted based on the application of 35 U.S.C. §112, sixthparagraph.

Referring now to FIG. 1, there is shown a pumping unit 100 consistentwith an embodiment of the present invention. The pumping unit 100includes: a driving section 190, a container 107 and pumping element180. Generally, pumping unit 100 is used for pumping cryogen to acryosurgical device such as, by way of non-limiting example, a cryogenicmedical treatment probe (not shown) which is connected to its outlet110.

The driving section 190 is a crank-follower mechanism that includes: arotating wheel 105 connected to a link 115 via a bearing 106 at an endof the link; and a follower 111 connected to another end of the link 115via a bearing 116.

The pumping section 180 includes: inlet plug 104, valve seat 102, bellow101, valve seat 103, and outlet plug 112 and is driven by the back andforth motion of follower 111.

The bellow 101 includes an inlet valve seat 102 and is submerged in acryogen 108. The inlet valve seat 102 is below the surface 130 of thecryogen 108 so that when inlet plug 104 travels away from the inlet seat102 (upward as illustrated in FIG. 1), cryogen 108 flows 131 into thebellow 101. It should be noted that surface 130 of the cryogen 108 maybe well above inlet plug 104. At the other end of the bellow 101,opposing the end with inlet opening 102 is an outlet valve seat 103 thatis not in direct fluid communication with the cryogen 108. Bellow 101 ismechanically connected to container 107 at or near outlet valve seat103. Relief valve 109 allows evaporation of the cryogenic fluid 108, andmaintains atmospheric pressure (or pressure slightly above atmosphericpressure) in the container 107. Preferably, container 107 is thermallyinsulated as known in the art of cryogenics.

When outlet plug 112 travels away from outlet opening 103 of bellow 101(downward as illustrated in FIG. 1), fluid in bellow 101 may exitsthrough outlet opening 103.

In operation, as the wheel 105 turns, for example in direction 117, suchthat bearing 106 is moving up, for example, the link 115 which isconnected to wheel 105 via bearing 106, forces the follower 111, whichis connected to link 115 via bearing 116, to move up. Follower 111 pullsboth inlet plug 104 and outlet plug 112 upwards such that inlet opening102 is opened and cryogen 108 enters 131 bellows 101 by gravitationalforce due to the condition of communicating vessels created betweeninner volume of bellows 101 and container 107.

As wheel 105 continues to turn such that bearing 106 reaches its highestposition and starts to descend, follower 111 pushes down inlet plug 104and outlet plug 112, closing inlet opening 102 and opening outletopening 103. As follower 111 continues to descend, bellows 101 iscompressed under the pressure of inlet plug 104 and the cryogen in thebellows is forced through the now opened outlet valve seat 103 and flows133 through outlet 110.

As wheel 105 continues to turn such that bearing 106 reaches its lowestposition and starts to ascend, the refilling of bellows 101 is repeatedas disclosed above. During the ascent of inlet plug 104 bellows 101expand due to its flexibility to accept the inflow 131 of cryogen 108.

Keeping driving section 190 out of container 107, and specificallykeeping the motor (not seen in these figures) that rotates wheel 105outside the cold environment may reduce heat leaks into the containerand heat generation inside the container, thus reducing evaporation andwaste of the cryogen.

Referring now to FIG. 2, there is shown a pumping unit 200 consistentwith an embodiment of the present invention. The pumping unit 200includes driving section 290, a container 207, and pumping section 280.Relief valve 209 allows evaporation of the cryogenic fluid 208, andmaintains atmospheric pressure (or pressure slightly above atmosphericpressure) in the container 207.

The driving section 290 is similar or identical to driving section 190that was depicted in FIG. 1.

In contrast to pumping section 180 of FIG. 1, wherein outlet plug 112 isconnected to, and operated by follower 111, controlling plug 212 whichis capable of closing outlet valve seat 203 is not operated by follower211 but instead it is responding to differences in cryogen pressureswithin bellows 201 and outlet 210. Alternatively, controlling plug 212is operated electrically in synchronization with the rotation of wheel205.

In operation, as the wheel 205 turns, for example in direction 217, suchthat bearing 206 is moving up, the link 215 which is connected to wheel205 via bearing 206, forces the follower 211, which is connected to ling215 via bearing 216, to move up. Follower 211 pulls inlet plug 204upwards such that inlet opening 202 is opened and cryogen 208 havinglevel 230 above inlet opening 202 enters 231 bellows 201 bygravitational force due to the condition of communicating vesselscreated between inner volume of bellows 201 and container 207. Duringthis refilling stage of the pumping cycle, controlling plug 212 closesexit opening 203 due to one or combination of the following:

-   1) The cryogen pressure in outlet 210 is greater than the pressure    in the container 207. This may be caused by flow resistance in the    path of the pumped cryoliquid exiting outlet 210, or by evaporation    of cryogen in the cryosurgical device connected to outlet 210. The    difference in pressures forces controlling plug 212 against outlet    valve seat 203;-   2) A spring (not seen in this figure) may be used for overcoming    gravity and forcing controlling plug 212 against outlet opening 203;-   3) Controlling plug 212 may be made such that its specific gravity    is lower than the cryoliquid such that it floats on cryogen in    outlet 210 and is pushed against outlet opening 203; and-   4) Controlling plug 212 may be electrically operated, for example    using a solenoid (not shown), in synchronization with the rotation    of 205.

As wheel 205 continues to turn such that bearing 206 reaches its highestposition and starts to descend, follower 211 pushes down inlet plug 204,closing inlet valve seat 202. As follower 211 continues to descend,bellows 201 is compressed under the pressure of inlet plug 204 and thecryogen the bellows forces open controlling plug 212 and flows 133through outlet 210. Alternatively, controlling plug 212 is electricallyopens to allow cryogen flow 133 through outlet 210.

As wheel 205 continues to turn such that bearing 206 reaches its lowestposition and starts to ascend, the refilling of bellows 201 is repeated.During the ascent of inlet plug 204 bellows 201 expand due to itsflexibility to accept the inflow 231 of cryogen 208.

Referring now to FIG. 3, there is illustrated a pumping unit 300consistent with an embodiment of the present invention.

The driving section 390, which is similar or identical to drivingsections 190 and 290 disclosed above includes: a rotating wheel 305connected to a link 315 via a bearing 306 at an end of the link; and afollower 311 connected to another end of the link 315 via a bearing 316.

The pumping section 380 includes: an inlet plug 304, an inner bellow301, an outer bellow 321, and an outlet plug 312 and is driven by thereciprocal motion of follower 311.

The pumping unit 300 differs from the pumping units 100 and 200 of FIGS.1 and 2, respectively, in that the pumping unit 300 includes a doublebellows (i.e., inner bellow 301 and outer bellow 321, with vacuum in thespace 331 between them to thermally insulate the cryogen in the innerbellows 301 from the environment. In this case, the bellows 301 and 321are not immersed in the container 307 filled with cryogen 308. Reliefvalve 309 allows evaporation of the cryogenic fluid 308, and maintainsatmospheric pressure (or pressure slightly above atmospheric pressure)in the container 307. The filling of the inner bellow by the law ofcommunicating vessels is permitted by fluid connection 341. The flexibleconnection 342 permits the relative motion of the valve seat 302 whichis connected to the bellows 301, and 321, and the cryogen container 307,while container 307, and outlet 310 with outlet valve seat 303, anddriving section 390 are fixed to the body of pumping unit 300.

In the exemplary embodiment depicted in FIG. 3, outlet plug 312 isconnected to, and operated by follower 311 to allow flow 133 of cryogenthrough outlet 310. This operation is a similar to the operation ofoutlet plug 112 depicted in FIG. 1. Alternatively, outlet plug 312 mayoperate similarly to the operation of plug 212 depicted in FIG. 2, thatis: outlet plug 312 may be operated electrically in synchronization withthe rotation of wheel 305; or outlet plug 312 may be responding todifferences in cryogen pressures within bellows 301 and outlet 310.

FIG. 4A schematically illustrates a cross sectional view of a pumpingunit 400 consistent with an exemplary embodiment of the presentinvention.

The pumping unit 400 includes: a driving section 490; a container 407;and a pumping section 480. Relief valve 409 maintains atmosphericpressure in the container 407 filled with cryogenic fluid 408, to permitthe filling of the bellow by the law of communicating vessels.

The driving section 490 includes: a rotating wheel 405 connected to alink 415 via a bearing 406 at an end of the link; and a follower 411connected to another end of the link 415 via a bearing 416.

The pumping section 480 includes a piston 401 that travels reciprocallywithin a cylinder 410 and that is driven by the reciprocal motion offollower 411.

In operation, as the wheel 405 turns in direction 417, the link 415forces the follower 411 to move cyclically in up and down directions. Aspiston 401, which is connected to follower 411 moves down from itsupmost position, it closes the opening 402 in cylinder 410, stopping thefilling of the cylinder 410 with cryogen 408 through opening 402 whichis below the level 430 of cryogen 408 in container 407, by law ofcommunicating vessels. As the follower continues to move downwardstoward a position of maximum displacement, the piston presses thecryogen in the cylinder 410 to exit through the check valve 403.

After the follower has reached its lowest position and is moving up,valve 442 in piston 401 opens, letting air flow through tunnel 441 inpiston 401, and compensate for the low pressure created by the movement,i.e. preventing vacuum pressure to be generated in cylinder 410 underpiston 401.

Alternatively, the tunnel 442 and valve 441 may be omitted and the smallgap between piston 401 and cylinder 410 may be configured to allow somegas flow into the cylinder 410. Same small gap between piston 401 andcylinder 410 is small enough to prevent excessive escape of cryogenicliquid during the down motion of the piston due to the higher viscosityof liquid in relation to the viscosity of gas. Additionally oralternatively, partial vacuum is generated in the cylinder 410 belowpiston 401 when piston 401 is moving up. This partial vacuum ispartially filled with vapor of cryogenic left in the bottom of cylinder410 and near check valve 403.

When piston 401 moves up, the inlet 402 is exposed to the cryogen 408 inthe container 407 allowing the fluid to fill the cylinder through inletopening 402, replacing any air that enter the cylinder 410, or vaporgenerated in it during the first part of the movement upwards.

FIG. 4B schematically illustrates enlarged cross sectional view ofpiston 401 showing tunnel 441, valve 442, and part of follower 411according to the exemplary embodiment of the present invention depictedin FIG. 4A.

FIG. 5A, schematically illustrates a pumping unit 500 consistent with anexemplary embodiment of the present invention. The pumping unit 500includes driving mechanism 590 and a pumping element 580.

The driving section 590 includes: a rotating wheel 505 connected to alink 515 via a bearing 506 at an end of the link; and a follower 511connected to another end of the link 515 via a bearing 516.

The pumping section 580 includes a piston 501 that travels reciprocallywithin a cylinder 510 and that is driven by the reciprocal motion offollower 511. Cylinder 510 is a double walled cylinder with an outerwall 507 and an inner wall 521. The two walls 507 and 521 of cylinder510 are separated by vacuum space 531 for thermal insulation.

Opening 502 in cylinder 510 is connected to a container (not shown) withcryogen.

Pumping unit 500 operates the same as system 400 seen in FIG. 4A. Thelink 515 forces the follower 511 to move in up and down directions. Apiston 501 connected to follower 511 closes the opening 502 as it movesdown, stopping the filling of the cylinder 510 with cryogen throughopening 502, by law of communicating vessels. As the follower continuesto move downwards, the piston presses the cryogen in the cylinder 510 toexit through the check valve 503. When the follower is moving up, theinlet 502 is exposed to the cryogen allowing the cryogenic fluid to fillthe cylinder 510 through inlet opening 502.

After the follower has reached its lowest position and is moving up,valve 542 in piston 401 opens, letting air flow through tunnel 541 inpiston 501, and compensate for the low pressure created by the movement(i.e. preventing vacuum pressure to be generated in cylinder 510 underpiston 501).

Alternatively tunnel 542 and valve 541 are missing. Instead, the smallgap between piston 501 and cylinder 510 allows some gas flow into thecylinder 510. Same small gap between piston 401 and cylinder 510 issmall enough to prevent excessive escape of cryogenic liquid during thedown motion of the piston 501 due to the higher viscosity of liquid inrelation to the viscosity of gas. Additionally or alternatively, partialvacuum is generated in the cylinder 510 below piston 501 when piston 501is moving up. This partial vacuum is partially filled with vapor ofcryogenic left in the bottom of cylinder 510 and near check valve 503.

When piston 501 moves up, the inlet 502 is exposed to the cryogen in thecontainer (not shown) allowing the fluid to fill the cylinder 510through inlet opening 502, replacing any air that enter the cylinder510, or vapor generated in it during the first part of the movementupwards.

FIG. 5B schematically illustrates an enlarged cross sectional view ofpiston 501 showing optional tunnel 541, valve 542, and part of follower511 according to the exemplary embodiment of the present inventiondepicted in FIG. 5A.

FIG. 6A schematically illustrates a cross sectional view of a pumpingunit 600 using a piston 601 with a groove 652 according to an exemplaryembodiment of the present invention.

Pumping unit 600 using a piston 601 with a groove 652 is an optionalconfiguration that may be used in pumping units 400 and 500 of FIGS. 4Aand 5A, respectively. The piston 601 is configured to include a groove651 that permits, by rotating the piston 601 to select position of thepiston in relationship with the opening 602, in which opening 602 isclosed as the piston moves down, thus selecting the amount of thecryogen that is pressed to the exit valve 603.

The orientation of piston 601 may be preset during manufacturing orcalibrating or adjusting the pumping unit. Optionally, additionally oralternatively, the orientation of the piston may be changed by rotatingfollower 611, which connected to the piston 611. For example, follower611 may comprise a manual or motorized actuator allowing changing therotational orientation of the piston 601 relative to opening 602,optionally while the pumping unit is assembled or in operation.

After the follower has reached its lowest position and is moving up,valve 642 in piston 601 opens, letting air flow through tunnel 641 inpiston 601, and compensate for the low pressure created by the movement,i.e. preventing vacuum pressure to be generated in the cylinder 610under piston 601.

Alternatively tunnel 642 and valve 641 are missing. Instead, the smallgap between piston 601 and cylinder 620 allows some gas flow into thecylinder 510. Same small gap between piston 401 and cylinder 610 issmall enough to prevent excessive escape of cryogenic liquid during thedown motion of the piston 501 due to the higher viscosity of liquid inrelation to the viscosity of gas. Additionally or alternatively, partialvacuum is generated in the cylinder 610 below piston 601 when piston 601is moving up. This partial vacuum is partially filled with vapor ofcryogenic left in the bottom of cylinder 610 and near check valve 603.

When piston 601 moves up, the inlet 602 is exposed to the cryogen in thecontainer (not shown) allowing the fluid to fill the cylinder 610through inlet opening 602, replacing any air that enter the cylinder610, or vapor generated in it during the first part of the movementupwards.

FIG. 6B schematically illustrates enlarged cross sectional view ofpiston 601 showing optional tunnel 641, valve 642, and part of follower611 according to the exemplary embodiment of the present inventiondepicted in FIG. 6A.

FIG. 7 illustrates an alternative driving section 700 that mayoptionally replace the driving sections in any of pumping units 100,200, 300, 400, and 500 of FIGS. 1-3, 4A and 5A, respectively. Thedriving section 700 includes a cam 705 instead of a wheel. The cam 705rotates in direction 717 around its pivot 706 and, because of its shape,drives a follower 715 reciprocally toward and away from the camresulting in translation of the rotational motion of the cam 705 intoreciprocating linear motion of the follower 715. The follower 715 isoptionally connected to follower 711 via a pivot 716. The follower 711,in turn, may drive either a piston or a bellows. Followers 715 or 711may act as followers 111, 211, 311, 411, 511 and 611 in FIGS. 1-3, 4A,5A, and 6A, respectively.

FIG. 8 illustrates pneumatic system, another alternative driving section800, which may optionally replace driving section 190, 290, 390, 490,590 or driving section 700. Pneumatic driving system 800 may optionallybe used in any of pumping units 100, 200, 300, 400, and 500 of FIGS.1-3, 4A, and 5A, respectively. The pneumatic driving section 800includes a piston 850 instead of a wheel or cam. With thisconfiguration, there is no need to translate rotational motion intoreciprocating linear motion. The piston 850 moves up and down dependingon the pneumatic pressure supplied at either opening 851 for motiondownwards, or at opening 852 for motion upwards. In operation, a link853, which is attached to an end of piston 850 optionally, pushes theoptional follower 811 through optional pivot 816. Follower 811, or link853 in turn, drives the pumping section. Pneumatic pressure is suppliedby a gas pressure source and controlling valves as known in the art,which are not seen in this figure. Alternatively, hydraulic power may beused. Follower 811 or link 853 may act as followers 111, 211, 311, 411,511 611 and 711 (or 715) in FIGS. 1-3, 4A, 5A, 6A and 7, respectively.

As described above, embodiments of the present invention provide acryogen pump with unique control of the inlet and outlet flow. Thesystem includes either a bellow pump or piston pump. The pump is eithersubmerged in cryogenic fluid, or vacuum insulated. The inlet of thefluid is applying the law of communicating vessels, eliminating the needfor an inlet valve.

Also, as described above, the cryogen pumps of embodiments of thepresent invention simplify the handling of the boiling fluid by eitherinsulating it from the environment with vacuum insulation, or submergingthe pumping unit in the bath of boiling fluid. In addition the inletuses the natural law of communicating vessels, eliminating the need fora check valve and smoothing the operation. The motion distance of theconnecting lever from the crank and the diameter of the crank positionalso can be used to make the pump metering pump. The pump can raise thepressure of the cryogens from atmospheric pressure or below to 40 at.The control of the pressure and the flow can be achieved by eitherchanging the speed of the motion of the pump or change in thedisplacement of the pressing element.

All the elements of the disclosed systems may be made from materialsuitable to withstand the low temperature and the function of theelements would not be compromised by the low temperature. The lowestdesign temperature is negative 220 degrees Celsius.

Examples of various features/aspects/components/operations have beenprovided to facilitate understanding of the disclosed embodiments of thepresent invention. In addition, various preferences have been discussedto facilitate understanding of the disclosed embodiments of the presentinvention. It is to be understood that all examples and preferencesdisclosed herein are intended to be non-limiting.

Although selected embodiments of the present invention have been shownand described individually, it is to be understood that at least aspectsof the described embodiments may be combined.

Although selected embodiments of the present invention have been shownand described, it is to be understood the present invention is notlimited to the described embodiments. Instead, it is to be appreciatedthat changes may be made to these embodiments without departing from theprinciples and spirit of the invention, the scope of which is defined bythe claims and the equivalents thereof.

1. A cryogen pump, comprising: a pump section that includes: a bellowwith an inlet opening at a first end and an exit opening, the inletopening in direct fluid communication with a volume of a cryogen, theexit opening at least in fluid communication with a second end of thebellow opposing the first end, a pair of plugs configured to sealinglyclose the opposing ends of the bellow, the pair of plugs cooperating sothat when one plug sealingly closes one of the ends, the other end ofthe bellow is open; and a drive section configured to drive the pumpsection in a reciprocating manner so as to move the plugs.
 2. The pumpof claim 1, further comprising a container configured to retain thevolume of a cryogen, wherein the bellow is submerged in the cryogen whenthe volume of cryogen is retained such that the inlet opening isdisposed in the cryogen, and wherein, when the inlet opening is in anopen condition, cryogen flows into the bellow.
 3. The pump of claim 1,wherein the bellow is a first bellow, and wherein the pump sectionincludes a second bellow surrounding the first bellow and spaced fromthe first bellow by a vacuum space that insulates the first bellow. 4.The pump of claim 1, wherein the drive section translates rotationalmotion into reciprocating, linear motion that is communicated to theplugs.
 5. The pump of claim 1, wherein the drive section includes apneumatic piston that yields reciprocating, linear motion that iscommunicated to the plugs.
 6. A cryogen pump, comprising: a pump sectionthat includes a cylinder having an inlet opening in communication with acryogen and an exit valve, and a piston having a tunnel extendingtherethrough, the piston configured to travel reciprocally in thecylinder along a travel axis therein between a load condition in whichthe piston is at a position of minimum displacement and the cryogenflows into the cylinder via the inlet opening and a compressingcondition in which the piston is at a position of maximum displacement,and the cryogen does not flow into the cylinder, and cryogen in thecylinder is compressed and pressed out of the exit valve; and a drivesection configured to drive the pump section in a reciprocating mannerso as to move the piston.
 7. The pump of claim 6, further comprising acontainer configured to retain a volume of cryogen, wherein the cylinderis substantially submerged such that the inlet opening is under a fluidlevel, and wherein the exit valve is not in direct fluid communicationwith a retained volume of the cryogen.
 8. The pump of claim 6, whereinthe cylinder is a double walled cylinder with two walls, the walls beingseparated by a vacuum space that insulates an interior one of the walls.9. The pump of claim 6, wherein the piston includes a groove thatpermits, by selective rotation of the piston with respect to the inletopening, selection of an amount of the cryogen that fills the cylinderwhen the piston is in the load condition.
 10. The pump of claim 6,wherein the drive section translates rotational motion intoreciprocating, linear motion that is communicated to the piston.
 11. Thepump of claim 6, wherein the drive section includes a pneumatic pistonthat yields reciprocating, linear motion that is communicated to thepiston.
 12. A pump, comprising: a cylinder having an inlet opening incommunication with a cryogen and an exit valve; and a piston having apressure compensation section, the piston configured to travelreciprocally in the cylinder in a range between positions of minimum andmaximum displacement, wherein the cryogen flows into the cylinder viathe inlet opening when the piston is at least near the position ofminimum displacement, wherein the cryogen does not flow into thecylinder when the piston is at least near the position of maximumdisplacement, and wherein the pressure compensation section includes apassage that extends through the piston.
 13. The pump of claim 12,wherein the passage permits a gas to flow out of the piston into thecylinder when the piston moves toward the position of minimumdisplacement.